This description relates to loudspeaker suspensions.
Referring to FIG. 1, a typical loudspeaker 14 includes a stiff cone 15 connected to a voice coil 20 at the apex of the cone. The loudspeaker 14 includes a dust cap 23 attached to the cone 15. The voice coil 20 interacts with the magnetic circuit formed from permanent magnet 25, back plate/pole piece structure 30, and top plate 21. When the voice coil is driven by an audio signal, the cone 15 vibrates axially to produce sound.
An outer edge 40 of the cone 15 is attached to a rigid basket 45 along an annular mounting flange 47 by suspension element 50, typically referred to as a surround. The voice coil 20 and/or apex of cone 15 may be attached to another section of the rigid basket 45 by second suspension element 35, typically referred to as a spider. The surround 50 is often made from a flexible material such as fabric, that allows the cone 15 to vibrate but provides a restoring force to aid in restoring the cone 15 to an at-rest position, when the voice coil 20 is not being driven. The spider 35 is typically a circular woven cloth part with concentric corrugations. The suspension elements 35, 50 provide a restoring force, along the axial direction, and a centering force, along the radial direction, for the cone 15. In many examples, single or multiple surrounds and/or spiders are used as suspension elements 35, 50.
Referring now to FIGS. 2 and 3, the prior art surround 50 can be seen to be a hollow semi-toroid about a center O with an inner circumferential edge 60 and an outer circumferential edge 55. As shown in FIG. 3, a cross-section taken along line A-A in FIG. 2 traces a semi-circular shape or a dome shape. In response to an axial force 58 on the cone 15, a point P on the surround 50 moves, for example, along a locus 59 defined by points P2-P-P1.
FIG. 4 shows a plan view of an alternative prior art surround 70. The surround 70 has grooves 65 extending outward at an angle to the radial direction, over the majority of the width from the inner to the outer circumferential edges of the surround.
FIG. 5 shows a circumferential section along line B-B of FIG. 3. Each groove can be a V-shaped trough D at the bottom and corners E, F at the top.